Vacuum compensating device for engine cooling system

ABSTRACT

An engine cooling system including a vacuum compensating device in fluid communication with the system. The compensating device maintains the cooling system full at all times and reduces stress on the system. A viewing device is substituted for the usual cap on the radiator filling neck to allow visual determination of the coolant level, and the viewing device seals the radiator. The invention also includes a unique vacuum compensating device including a rigid enclosure and a vacuum and pressure relief valve mounted on the enclosure to maintain pressure in the system within safe, predetermined limits. In the preferred embodiment, the enclosure is elongated, is of a relatively small diameter, and is mounted generally upright so only a small surface area of coolant is exposed to air when the coolant is cold and the vacuum relief valve opens.

United States Patent 72] Inventor Allie B. Holmes Corpus Christi, Tex.

[21] App]. No. 4,834

[22] Filed Jan. 22, 1970 [45] Patented Nov. 2,1971

[73] Assignee Opti-Cap Inc.

Corpus Christi, Tex.

Continuation-impart of application Ser. No. 762,254, Sept. 16, 1968, now Patent No. ,521,702, dated July 28, 1970.

[54] VACUUM COMPENSATING DEVICE FOR ENGINE COOLING SYSTEM 16 Claims, 15 Drawing Figs.

[52] US. Cl. 165/51, 165/111, 123/178 [51] Int. Cl F28b 3/00 [50] Field of Search 165/51, 111,132;l23/4l.27,41.15,4l.14,178

[56] References Cited UNITED STATES PATENTS 2,086,441 7/1937 Rushmore 123/178 2,878,794 3/1959 Stromberg 123/4127 3,096,748 7/1963 Harry l23/4i.15 3,265,048 8/1966 Herbon 123/4Ll4 3,077,927 2/1963 White et al. l65/l32 Primary Examiner-Charles Sukalo Att0rney M arkva, Smith & Kruger ABSTRACT: An engine'cooling system including a vacuum compensating device in fluid communication with the system. The compensating device maintains the cooling system full at all times and reduces stress on the system. A viewing device is substituted for the usual cap on the radiator filling neck to allow visual determination of the coolant level, and the viewing device seals the radiator. The invention also includes a unique vacuum compensating device including a rigid enclosure and a vacuum and pressure relief valve mounted on the enclosure to maintain pressure in the system within safe, predetermined limits. In the preferred embodiment, the enclosure is elongated, is of a relatively small diameter, and is mounted generally upright so only a small surface area of coolant is exposed to air when the coolant is cold and the vacuum relief valve opens.

PATENTEDHOV 2 Ian 3.616.847

SHEET 10F 5 444/: 5. 5 04/1459 Mfiyam BY f y 114% ATTORNEY VACUUM COMPENSATING DEVICE FOR ENGINE COOLING SYSTEM This is a continuation in part of pending application Ser. No. 762,254, filed Sept. 16, 1968 for Vacuum Compensating Device for Engine Cooling System and Method of lnstalling and now U.S. Pat. No. 3,521,702 granted July 28, 1970.

This invention relates to an improved engine cooling system which is maintained full of liquid coolant at all times during normal operation, whereby the cooling system operates at maximum efficiency.

The invention also relates to a cooling system including an improved compensating device which automatically compensates for vacuum created in the cooling system when the engine is off and the coolant cools, but which maintains the cooling system full of coolant regardless of engine operating conditions within a normal range.

The usual engine cooling system includes a water jacket associated with the engine and usually formed integral with the engine block, a radiator or heat exchanger mounted adjacent the engine block, a radiator or heat exchanger mounted adjacent the engine and through which the coolant from the engine is circulated, a circulating device such as a water pump which circulates the coolant, and in the case of most automotive vehicles, a fan which draws air through the radiator to cool the coolant.

Most presently available American automobiles have radiators of the upright type which include a heat exchanger core, and upper and lower end tanks connected to the core. Theengine cooling jacket has an outlet, and an inlet at a lower elevation than the outlet. Coolant is circulated'by the water pump from an upper outlet of the engine cooling jacket to the top of the radiator, then downwardly through the radiator core, and then from the bottom tank of the radiator to the inlet of the engine cooling jacket. Since the flow through the radiatoruis from top to bottom and since the temperature of the coolant is reduced as it flows through the radiator this system utilizes nonnal convection flow of the liquid coolant to assist the water pump circulation of the coolant through the system. Since liquid coolant becomes less dense as it is heated, there is also a natural convection'flow of the coolant from thelower elevation inlet of the engine cooling jacket to the higher elevation outlet.

Internal combustion engines operate most efiiciently when the temperature of the coolant leaving the cooling jacket outlet is approximately l80 F. However, since an engine cooling system must be of sufficient size to maintain the coolant entering the engine at a temperature below the optimum l80F., under any expected operating conditions (such as when ambient temperatures are as high as F.) a thermostat is usually provided at the outlet of the engine cooling jacket and functions to limit flow through the engine if the temperature of the coolant is lower than optimum.

For the cooling system to operate most efficiently, the system should be completely full of coolant. Present day cooling systems are of the pressurized type in which the coolant is maintained under a positive pressure of from 8 to p.s.i. above atmospheric pressure. With the coolant under this higher pressure, the boiling temperature of the coolant is increased to substantially more than the 212 F. boiling point of water at sea level pressure. If it were possible to operate an internal combustion engine continuously, the radiator could be completely filled with coolant, while the engine is hot, and the cooling system would then operate at optimum efficiency. However, in the case of the usual automobile or other motor vehicle engine, the engine is not running continuously, but is frequently started and stopped. Each time the engine is stopped for any considerable time, the coolant cools from the optimum operating temperature of 180 F. to the ambient temperature, which, for purposes of illustration, shall be taken as 70 F. Such cooling causes contraction of the coolant, and a substantial vacuum would be created within the cooling system were it not for the usual vacuum relief valve which is incorporated in the radiator cap of a pressurized cooling system and which opens as soon as a vacuum is present in the system. Thus, each time the engine cools, the vacuum relief valve opens and air is drawn into the cooling system. Then, when the engine is started and the coolant is again heated, the vacuum valve closes and pressure begins to build up in the system almost immediately. Since, as the incompressible coolant expands, the air drawn into the cooling system must be expelled, the overpressure relief valve of the radiator cap opens to release this air. However, this air is not really air but is in fact a vapor, which is present in the air or headspace at the top of the radiator. Hence, when the overpressure valve opens to release the air, as the coolant expands, some coolant is lost each time the coolant is heated.

Should the owner of the motor vehicle neglect to add coolant, problems of overheating occur. This is especially true where the vehicle is equipped with air conditioning and other power equipment driven by the engine. In addition, all automobiles manufactured after Jan. 1, 1969 are subject to strict air-pollution control requirements. At least one of the acceptable pollution control systems requires relatively high coolant temperatures to assure substantially complete combustion of a relatively lean air-fuel mixtureaHence, there is a smaller coolant temperature difference between normal operation and overheating than with prior automobile engines, and correspondingly, problems of overheating occur quite frequently in many new cars.

Another shortcoming of the known automotive cooling systems is that the buildup of pressure within the cooling system occurs ata time when the cooling system is in the poorest state to accommodate the pressure, namely, before the various partsof the system reach optimum operating temperatures. When these parts are cold, or only slightly warm, there is a tendency for the usual rubber hoses to be less resilient and hence, more apt to develop cracks than when the coolant is first heated. in addition, the various clamp connections of the cooling system, such as between the hoses and the radiator or engine block, are in a contracted state and hence are much more'likely to leak at low temperatures than at the normal operating temperature of the cooling system. This is especially true where the coolant contains a glycol-base an tifreeze which has a wetting action andis much more likely to leak through minute openings than when water is the coolant.

Another recently developed cooling system is the crossflow type where flow of liquid coolant through the radiator is horizontallyfrom one side to the other. Such crossflowradiators have gained acceptance by some manufacturers because they have a smaller vertical height and thus permit designing the automobile with a lower hood line, since the radiator is customarily mounted adjacent the front of the automobile. For crossflow-type radiators to operate efficiently, these radiators must be maintained full of coolant. Hence, an auxiliary radiator tank is provided in the vehicle at a location above the level of the top of the radiator and a large diameter conduit connects. the auxiliary tank to the radiator. The auxiliary tank is usually provided with the normal radiator filling neck which isclosed by a radiator pressure-vacuum cap in the usual manner. Within this auxiliary tank, the same conditions prevail as at the top of the upright-type radiator, namely, the coolant fills the tank when it is heated and expands, but contracts and draws air into the tank via the radiator cap vacuum valve, as it cools.

IN MY U.S. Pat. No. 3,307,620, granted Mar. 7, 1967, there are disclosed several embodiments of vacuum relief devices for engine cooling systems which function quite well to prevent the undesirable pressure buildup and introduction of air into cooling systems of internal combustion engines. The present invention represents improvements over that system which provide for better durability and reliability of the vacuum compensating device, simplify installation of the vacuum compensating device, and more readily adapt the vacuum compensating device for use with the modern automobile which has limited space in the hot engine companment and in which mounting of even small accessories where the vehicle is equipped with such devices as air conditioning and power steering is quite difficult.

The improved attachment, in accordance with this invention, takes the form of an elongated cylinder or canister which advantageously is connected to the radiator by a small diameter tube or hose that communicates with the interior of the canister. The canister itself is rigid to provide a liquidtight enclosure. This enclosure is elongated and of relatively small diameter but is of sufficient volume to contain coolant to maintain the engine cooling system full during normal expansion and contraction of the coolant when the engine is started and subsequently turned off. The canister is so mounted that the tube or hose from the radiator connects to the canister at an elevation lower than its opposite or top end which is provided with a filling opening in the form of the usual radiator filling neck. The filling neck of the canister is closed by a radiator cap which includes a vacuum relief valve as well as a pressure relief valve for the system. Depending on the relative elevation of the canister to the portions of the engine cooling system, the filling neck on the compensating device may facilitate filling the cooling system of the engine.

In the engine cooling system equipped with this vacuum compensating device, a special radiator-type cap is used to close the filling opening of the attachment. This radiator cap is considered special because its vacuum relief valve is set to open only when the vacuum in the cooling system exceeds a value of about 1-3 p.s.i. below atmospheric pressure. The filling neck of the radiator of the cooling system with which the compensating attachment is used is sealed by a transparent viewing cone which seals against the usual sealing flange of the radiator neck. This viewing cone extends into the radiator tank a sufficient distance to enable one to merely look at the viewing cone and positively ascertain that the radiator is full of coolant. Advantageously, the viewing cone is maintained in sealed relation with the sealing flange of the radiator neck by a compression spring selected to allow the cone to act as an overpressure relief valve, and the spring is so selected that the pressure at which the viewing cone functions to relieve excess pressure is slightly higher than the pressure at which the normal pressure relief valve of the cap on the compensating device opens. Hence, in the event that an abnormal condition occurs within the radiator which causes pressures sufficient to open the pressure relief valve on the compensating device, the overpressure valve on the radiator neck will not normally open. However, since the compensating attachment is connected to the cooling system by a relatively small diameter hose, pressure may not be able to escape through the compensating device. Under these conditions, the viewing cone valve will open to prevent explosion or other damage to the cooling system of the engine.

By sealing both the radiator neck and the compensating device opening, sufficient vacuum is created within the cool ing system each time the coolant cools to assure that liquid coolant in the compensating device is drawn or sucked back into the cooling system to maintain the system full.

As the engine warms up and the coolant is heated, pressure builds up in the system. ideally, there should be no positive pressure in the system until the coolant reaches the optimum operating temperature. With applicant's improved arrangement, the system is maintained full of liquid coolant both when the coolant is cold and when the coolant is heated to normal operating temperatures. Hence, when the coolant is cold the compensating device canister may be only partially full but the cooling system is completely full of liquid. When the coolant is at its normal operating temperature, the canister is filled with coolant and the air previously above the coolant in the canister has been expelled through the pressure relief valve radiator cap at the upper end of the canister. In practice, however, it has been difficult to maintain both the compensating device and the cooling system completely full of coolant during normal operating conditions. lnstead, a slight amount of air is usually in the upper end of the compensating device adjacent the radiator cap that closes the device. This slight amount of air does not, however, adversely affect the operation of the compensating device, but in fact improves its operation because the air expands somewhat when the coolant cools, and hence, opening of the vacuum valve is delayed. Conversely, the air above the liquid coolant in the canister, when the coolant is cold, is compressed somewhat as the coolant temperature increases and hence, provides space for some expansion of the coolant before the pressure relief valve opens.

Correspondingly, an object of this invention is to provide an improved cooling system including a vacuum compensating device having a vacuum relief valve on the compensating device to create a vacuum in the cooling system to assure return of liquid coolant to the system to maintain it full while protecting the cooling system against excessive vacuum and excessive entry of oxygen containing air.

Another object is an improved vacuum compensating device for a cooling system which is particularly adapted to be mounted in the engine compartment of a motor vehicle;

Another object is a vacuum compensating attachment for an internal combustion engine, the attachment being rugged and durable and having provision for maintaining the cooling system proper full of liquid coolant at all times, thereby eliminating air from the cooling system proper and providing for operation at maximum efficiency;

Another object is a vacuum compensating device which can readily be connected to an already manufactured cooling system for an engine, and therefore, the compensating device can be used with any existing engine cooling system;

A further object is an improved compensating device for an engine cooling system, and which is inexpensive to manufacture, long lasting, and which is tubular and elongated to facilitate mounting same in the crowded engine compartment of the modern automobile;

Another object is an improved cooling system including a vacuum compensating device in the form of a rigid enclosure having its lower end in communication with the engine cooling system and including a vacuum relief valve and pressure relief valve adjacent its upper end;

A further object is an improved engine cooling system including a vacuum compensating device in the form of a rigid elongated cylinder or canister, the canister being of sufficient strength to withstand the normal operating pressures of the cooling system and including a vacuum relief and pressure relief valve adjacent an upper end of the compensating device.

A still further object is an internal combustion engine cooling system in which a vacuum compensating device communicates with the cooling system, a first pressure relief valve seals the normal radiator opening of the cooling system, a second pressure responsive valve seals an upper end of the compensating device, and a vacuum relief valve adjacent the upper end of the compensating device protects the entire cooling system against excessive vacuum caused by cooling of the liquid coolant.

Another and further object is an improved engine cooling system in which a vacuum compensating device including a rigid enclosure communicates with the cooling system, vacuum and pressure relief valve means close the rigid enclosure, and second vacuum and pressure relief valve means seal the radiator filling neck of the system to provide for fail safe operation, thereby completely protecting the cooling system against excessive vacuum and overpressure while maintaining the system proper full of liquid coolant for maximum operating efficiency at all times.

Numerous other features and advantages of this invention will become apparent with reference to the accompanying drawings which are illustrative of the preferred embodiments of the features of this invention, and in which:

FIG. I. is a pictorial view of the engine compartment of a motor vehicle showing the vacuum compensating device of this invention mounted on a sidewall of the engine compartment and connected to the radiator for the engine;

H6. 2 is a view in longitudinal section of a first embodiment of the vacuum compensating device;

FIG. 3 is a transverse sectional view taken along line 3-3 of FIG. 2;

FIG. 4 is a partial sectional view of the lower end of the vacuum compensating device of FIG. 2 with portions removed for clarity of illustration;

FIG. 5 is a partial view in section of a radiator showing a transparent viewing element sealing the radiator opening;

FIG. 6 is a view corresponding to FIG. 5 showing a different embodiment of transparent viewing device sealing the radiator opening;

FIG. 7 is a partial view in section of the radiator showingthe connector by which the vacuum compensating device is connected to the radiator;

FIG. 8 is a schematic view in section showing the level of coolant in the radiator and the first embodiment of the compensating device when the coolant is at normal operating tem perature;

FIG. 9 is a view corresponding to FIG. 8 and showing the level of the coolant in the radiator and the first embodiment of the compensating device when the coolant is cold;

FIG. l0is a graph showing the relationship of coolant temperature and pressure in a conventional pressurized cooling system properly filled with coolant;

FIG. 11 is a graph showing the relationship of coolant temperature and pressure in an engine cooling system properly filled with coolant and equipped with the first embodiment of the vacuum compensating device of this invention;

FIG. 12 is a view corresponding to FIG. 2 and showing a second embodiment of the vacuum compensating deviceof this invention;

FIG. 13 is a schematic view in section sowing the level of coolant in the radiator and compensating device of FIG. 12 when properly filled with coolant and when the coolant is at. normal operating temperature;

F I6. 14 is a view corresponding to FIG. 13 and showing the level of the coolant in the radiatorand compensating device of FIG. 12 when the coolant is cold; and

FIG. 15 is a graph showing therelationship of coolant temperature and pressure in an engine cooling system equipped with the second embodiment: of the compensating device of this invention.

Referring now to the drawings in detail and particularly to FIG. 1, there is shown the engine compartment 1 of an automobile 2. Located within the engine compartment is an engine 3 having the usual water cooling jacket, and a heat exchanger or radiator 4 mounted in the forward portion ofengine compartment 1' immediately behind grill 5. The outlet of: the water jacket of engine 3 connects to the upper tank 6 of radiator 4 via a radiator hose 7; The liquid coolant in the. system flows through upper hose 7 to upper tank 6, then through core 8 of the radiator and ultimately back out ofthe lower tank 9 of the radiator and through lower hose 10 which is connected to the inlet of the water jacket of motor 3.

Mounted in the engine compartment is a vacuum compensating device 11. The vacuum compensating device is secured to inner wall 12 of the engine compartment by suitable screws threaded into the wall and which pass through thestraps of mounting bracket assemblies 13 and 14. As shown, compensating device 11 is mounted in a generally upright position and is connected to the top tank 6 of the radiator by a tubular conduit in the form of a heater hose 15, one endof hose 15 beingclamped to a connector assembly 16 extending through the side of upper tank 6. of the radiator. Advantageously, the vacuum compensating device 11 is mounted within engine compartment 1 so that a substantial portion of the compensating device is below the level of the top of radiator 4.

The upper end of vacuum compensating device 11 is closed by a radiator cap assembly 17 which includes an overpressure relief valve and a vacuum relief valve. The vacuum relief valve of cap 17 is adjusted to open only when the vacuum within the engine cooling system exceeds l-2 p.s.i. below atmospheric pressure.

The filling neck of radiator 4 is sealed by a radiator closure assembly 18 which advantageously includes a transparent viewing element 19. Advantageously, the cap portion 20 of closure assembly 18 is fixed to the radiator against removal, as by wiring the cap in position. Fixing the cap against removal prevents its inadvertent removal by a gasoline station attendant attempting the check the coolant level in radiator 4, who does not realize the closure assembly includes a viewing cone l9. Closure assembly 18 will subsequently be described in detail, and a modified version of the closure assembly will be described.

FIG. 2 shows vacuum compensating device 11 in longitudinal section. The compensating device has an elongated cylindrical canister portion or sleeve 21 formed from sheet metal. Sleeve 21 has a rigid body portion 22 provided with several vent openings 23 that extend through the body portion and prevent pressure buildup between sleeve 32 and tubular liner 24. A plurality of axially extending equally circumferentially spaced slots 25 are providedin lower end portion 26 of sleeve 21. Slots 25 originate at lower end edge 27 and extend axially a short distance along the sleeve; Slots 25 define a plurality of flexible tabs or fingers 28 with inwardly bent tips 29. Fingers 28 are free to flex, and thus, lower end 26 of the sleeve is flexible.

Upper end 30 of sleeve 21 is identicalto lower end 26 and includesa plurality of flexible fingers separated by slots that extend from upper end edge 31- of the sleeve. Hence, upper end 30'of the sleeve is flexible. Sleeve 21 is advantageously formed from a flat-piece of sheet metal by first cutting the slots 25, punching. vent openings 23, and forming bent tips 29, while the sheet is in its flat state. Then, the sheet is rolled to cylindrical form and the edges are joined along an interlocked double seam 32.

Tubular liner 24 takes the form of a tube of thin-walled flexible material which may be resilient. Advantageously, the material of liner 24 is a rubber, unaffected by temperatures as high as 250 F., which may sometimes be encountered during abnormal operation of an engine cooling system.

Liner 24, has a relaxed outside diameter which is somewhat greater than theinside diameter of sleeve 21. Hence, when the liner is relaxed as shown at FIGS. 2 and 3, the liner tends to bulge inwardly alongfolds 33, asillustrated.

As shown at FIG. 2, liner 24 is longer than sleeve 21 so its lower end portion 34 can be turned upwardly over lower end edge 27. End. portion 34 is concentric withlower end 26 of sleeve 21 and extends along and engages the outside surface of lower end 26. Similarly, upper end 35 of the sleeve is turned outwardly over upper end edge 31 and extends along and engages flexible upper end 30 of the sleeve. A reinforcing band 36 extends between liner 24 and flexible lower end 26 of the sleeve to prevent damage to the liner by the fingers at the lower end of the sleeve. Band 36 is formed from rubber at least as thick as the rubber of liner 24. Similarly, a reinforcing band 37 identical to band 36, extends between flexible upper end 30 of the sleeve and liner 24.

The upper end of compensating device 11 is closed by a cup-shaped'member 38 having a cylindrical sidewall 39 and a flat end wall 40. Sidewall 39 has a beveled inner end 41 to prevent damage to liner 24. End wall 40 has a suitable centrally located opening to receive the lower end of a radiator neck 42. Radiator neck 42 takes the form of an upright receptacle having a sidewall 43 and an overflow opening 44 formed in the sidewall and via which coolant expelled from compensating device 11 may readily flow from the filling neck. At the upper end of sidewall 43 is the usual bayonet slot cam connector 45 of a radiator filling neck. The lower end of filling neck 42 has a generally flat annular sealing flange 46.

As shown at FIG. 2, sidewall 39 of end member 38 as a diameter to be snugly received within the upper end of liner 24. End member 38 is sealed to liner 24 by a screw clamp.47 which encircles end portion 35 of the liner. Clamp 47 exerts a radially inward force on upper end 35 of the liner which is transmitted to flexible upper end 30 of the sleeve, then to band 37, and then' to inner end portion 48 of the liner, to tightly clamp inner end portion 48 into sealing engagement with the outside surface of sidewall 39 of end member 38.

The lower end of compensating device 11 is closed by a cup-shaped lower end member 50 which has a cylindrical sidewall 51 integral with a flat end wall 52. Sidewall 51 has a beveled inner end 53 which is smoothly rounded to prevent damage to inner end portion 54 of the liner. End wall 52 is provided with a nipple 55 which extends through an opening in the end wall and is secured to the end wall by solder 56. Nipple 55 has a diameter to be inserted in the end of heater hose 15, whereupon the end of the heater hose is secured to the nipple by a screw-type hose clamp 57.

Lower end member 50 is secured to the lower end of compensating device 11 in a manner identical to that explained for upper end member 38. Screw clamp 58 extends around external end portion 34 and transmits the radial compressive force from clamp 58 to flexible lower end 26 through reinforcing band 36 to clamp lower end 54 of the liner into tight sealing engagement with the exterior of sidewall 51 of lower end member 50. Since lower end 26 of sleeve 21 is flexible, as previously explained, this lower end is compressed by the clamp and a tight leak-free seal is obtained between the sidewall and the inner end portion 54 of the liner. The inwardly extending tips 29 of fingers 28, at the lower end of sleeve 21, prevent displacement of lower end member 50 axially outwardly of the compensating device, even when substantial pressures are present within the compensating device.

Filling neck 42 of the compensating device is closed by radiator cap 17. Cap 17 has a cap portion 58 adapted to lock onto the cam lock portion 45 of the filling neck. A sealing disc 59 at the lower end of cap assembly 17 is spring urged into sealing engagement with annular sealing flange 46 by a helically wound compression spring 60. Disc 59 is provided with a suitable annular gasket 61 which assures a liquidtight seal between the disc 59 and flange 46. Spring 60 and disc 59 function as an overpressure relief valve, disc 59 opening upwardly against the action of spring 60 in response to a predetermined pressure within compensating device 11.

Closing a central opening in disc 59 is a vacuum relief valve 62 comprised of a movable valve element 63 urged upwardly against the underside of disc 59 by a compression spring 64. Spring 64 and valve element 63 are so selected that the valve element 63 does not open until after a vacuum of l-2 p.s.i. is present in compensating device 11. Hence, sufficient vacuum will be created within compensating device 11, upon cooling of the coolant in the engine cooling system to assure inward contraction of tubular liner 24 so it follows the coolant in the system. However, in the event that an abnormal condition is encountered and the vacuum in the system exceeds a safe level of l or 2 p.s.i., valve element 63 will open to prevent collapse of the delicate core 8 of radiator 4.

FIG. shows the closure assembly 18 which seals radiator neck 70 of radiator 4. Radiator neck 70 has the usual upright sidewall 71 which forms a receptacle. The lower end of sidewall 71 is integral with a flat annular sealing flange 72. Viewing cone 19 has a conical body 73 which extends into coolant 74 in the radiator, and a flange 75 which extends radially outwardly trom the upper end of conical body 73. A resilient gasket 76 is interposed between the lower surface of flange 75 and the upper surface of sealing flange 72. A com pression spring 77 extends between cap and the upper surface of flange 75 to maintain viewing cone 19 in sealed relationship with the sealing flange 72. Cap 20 has a central opening so the interior of conical body 73 can b3 viewed to determine the coolant level without removing the cap. At the lower end of conical body 73 is a cylindrical tip 78 closed by an integral end 79. A vent opening 80 is formed through the wall of tip 78, and this opening is normally maintained closed by a wide elastic band 81 that extends around cylindrical tip 78. As described in my US. Pat. No. 3,276,488, closure assembly 18 can also be used to fill the cooling system of the vehicle without removing cap 20 by inserting a flexible hose into the interior of conical body 73.

FIG. 6 shows a closure assembly 18' which can be used to seal radiator neck 70 of radiator 4, in lieu of closure assembly 18. Here, viewing cone 85 terminates at a closed conical tip 84, and the conical body 86 of the viewing cone extends into coolant 74 in radiator 4. Flange 87, at the upper end of the conical body 86, is urged into sealing engagement with sealing flange 72 of the radiator neck. A gasket 88 is interposed between sealing flange 72 and flange 87 to assure a tight seal. Cap 20 has a central opening to permit viewing the interior of cone 86 and the cone is pressed into sealing engagement with sealing flange 72 by compression spring 77.

Because of the action of spring 77 of closure assembly 18, viewing cone 19 cooperates with the spring to provide an overpressure relief valve with the viewing cone acting as the movable valve element and unseating from sealing flange 72 in response to pressure within radiator 4 above a predetermined value. Advantageously, spring 77 is so selected that the pressure at which viewing cone l9 unseats from sealing flange 72 is slightly greater than the pressure at which the overpressure relief valve of cap assembly 17 releases. Preferably, closure assembly 18 releases overpressure at a value of mo 1 p.s.i. above the release value of the overpressure valve cap assembly 17.

Similarly, closure assembly 18 also functions as a pressure relief valve and spring 77 is again so selected that cap assembly 18 releases overpressure of a value Vz-l p.s.i. above the overpressure release value of cap assembly 17.

FIG. 7 shows connector assembly 89 extending through an opening 90 of wall 91 of upper tank 6 of radiator 4. Connector assembly 89 includes an externally threaded tube 92 which comprises the body of the connector, and a metal washer 93 secured to the inner end of the tube as by soldering. Between washer 93 and wall 91 of the radiator is a resilient annular sealing gasket 94. A second resilient annular sealing gasket 95 extends over tube 92 and engages the outside of wall 91. A washer 96, freely slidable along tube 92, is disposed on the tube, and an internally threaded nut fastens the connector to wall 91. As nut 97 is tightened, washers 93 and 96 are compressed to seal tube 92 at opening 90 through wall 91. Tube 92 has a diameter to receive hose 15 which is slipped over the projecting end of the tube and secured to the tube in sealed relation thereto by a screw clamp 98.

FIG. 8 shows the level of coolant in radiator 4 and vacuum compensating device 11 when the engine is at normal operating temperature and the coolant entering upper tank 6 of the radiator is at the usual temperature of 180 F. It will be observed, with reference to FIG. 8, that coolant 74 completely fills both radiator 4 and vacuum compensating device 11. The shown condition of the radiator and compensating device is an ideal condition in which the cooling system is completely filled wit coolant. However, the vacuum compensating device may have a small amount of air, such as air adjacent its upper end when the engine is at operating temperature. This small amount of air 110 is air which is difficult to remove from the system and is usually air which is trapped in the engine block and does not escape for some time after the cooling system is filled and sealed.

In FIGS. 8 and 9, connector assembly 89 is installed in the radiator so it extends through the top wall of top tank 6, and hence, communicates with the very top of the radiator. When the compensating device communicates with the top of the radiator, any air which leaks into the cooling system will be discharged to the compensating device the next time the coolant is heated, and will then be discharged through cap 17. The introduction of additional fresh air, which contains oxygen, would be deleterious to the system and ultimately could cause corrosion which would at least require adding a rust inhibitor or refilling the system with fresh coolant. However, as previously explained, air is not drawn into the system as the coolant cools. Such introduction of air is prevented by the vacuum valve 62, previously described for closure assembly 17, which maintains a low vacuum in the cooling system.

With coolant 74 at its operating temperature, there is a positive pressure in the cooling system which presses liner 24 into engagement with sleeve 21. The sleeve 21 contains the liner against overexpansion as a result of pressure in the system.

space within the compensating device is still substantially filled with coolant 74. This is because liner 24 has contracted to compensate for the reduction in volume ofthe coolant, when the coolant is cold. However, it will be observed with reference to FIG. 9 that radiator 4 is still completely filled with liquid coolants'74 and hence, the cooling system willoperate at maximum efficiency when the engine is again started and the coolant is heated to the normal operating temperature of the engine.

It must be appreciated that closure assembly 28 seals the filling opening in the neck 70 of radiator 4 and hence, a vacuum can .be created within the radiator to draw coolant 74 from compensating device 11 as the coolant contracts with a decrease in temperature. As previously explained, the vacuum valve of closure assembly 18 opensat a vacuum within the system which is greater than the vacuum in the system required to open the vacuum valve of cap assembly 27. Hence, as the coolant contracts and its temperature decreases below a predetermined value, the vacuum in radiator 4 will drawcoolant from the compensating device into the radiator and hence, the radiator will always be maintained full of liquid coolant, so long as the system operates normally.

FIG. shows graphically, the relationship between pres sure and temperature of coolant in a conventional pressurized cooling system properly filled with liquid coolant. Assume that the ambient temperature is 70 F and there is air in the upper tank of the radiator as a result of contraction of the coolant from operating temperature. As the coolant heats, the pressure of the coolant immediately increases in direct proportion to the increase in temperature until the overpressure relief valve of the radiator pressure cap is reached. Then, the overpressure valve opens and vents air, and usually some coolant vapor to atmosphere and thevalve continues to pop off until the coolant reaches its normal operating temperature, of about 180 F. When the coolantagain cools, air is drawn into the radiator through the vacuum valve which, in the standard radiator cap, opens in response to even a slight vacuum in the cooling system.

As shown at FIG. 10, with the ambient temperature at 70 F., the coolant expands a sufficient amount during heating that the coolant is under apressure of p.s.i. (above atmospheric pressure) when the coolant temperaturereaches l30 F. When the ambient temperature is 100, the system will not be pressurized to l5 p.s.i. until the coolant temperature reaches 160 F., whereupon the pressure cap will "pop of and maintain the pressure at l5 p.s.i. This 15 p.s.i. pressure is then maintained by the pressure relief valve of the radiator cap until operating temperature is reached.

Now consider FIG. 11 which shows the pressure within the cooling system of an engine equipped with vacuum compensating device 11 of this invention. As shown at FIG. 9, with the coolant cold, liner 24 is contracted and there is little if any air in the space above the coolant in the compensating device. Also, there is no air at all in the upper tank 6 of radiator 4. By virtue of the action of the tubular liner 24, there is a slight negative pressure or vacuum in the cooling system. However, this negative pressure is negligible at this time because atmospheric pressure acts on the outside surface of liner 24 via the vent openings 23 to maintain the liner in contact with the remaining coolant in the vacuum compensating device. The initial expansion of the coolant, as its temperature increases, is compensated for by the liner 24 which merely expands outwardly and hence, the pressure within the cooling system is initially only very slightly greater than atmospheric. Thus, the cooling system is not exposed to any substantial pressure above atmospheric. As the coolant continues to expand with increased temperature, the coolant ultimately fills the liner 24 and it is pressed against the inside of sleeve 21. Only after the liner is pressed against sleeve 21, and is contained against further expansion by the sleeve, does the pressure within the cooling system begin to rise. However, the pressure rises at a far more rapid rate per degree of increase of coolant temperature since there is little, if any air in the system. Hence, the cooling system equipped with compensating device 11 of this invention normally operates at lower pressure than the normal pressurized radiator systems. However, when the temperature of the coolant nears its boiling point, or the limit of its expan- 1 sion, the pressure in the compensating device equipped system increases rapidly, and correspondingly, the boiling point of the coolant is increased by the higher pressure in the system. Hence, pressures in the compensating device equipped system increase to a level approaching the 15 p.s.i. pop off" pressure of the overpressure relief valve only when the higher pressure is needed to prevent boiling of the coolant. Only when an abnormal condition occurs within the radiator, such as boiling of the coolant, does the pressure within. the cooling system reach the 15 p.s.i. above atmospheric pressure required to operate the overpressure relief valve. Hence, the advantage of the vacuum compensating device 11 of this invention is to maintain a substantially lower pressure within the cooling system while still'maintaining the radiator substantially full of liquid coolant at all'times for most efiicient cooling of the engine.

FIG. 12 shows a second embodiment of the compensating device of this invention. Compensating device 211 has an elongated thin=walled cylindrical canister portion or sleeve 22ladvantageously formed from metal and which is quite similarto'the canister or sleeve 21 previously described with reference to FIGS. 2-4. Sleeve 221 has a rigid body portion 222 which is continuous and imperforate and of sufiicient strength to withstand the pressure and vacuum to which the engine cooling system is subjected. The lower end 226 of sleeve 221 is identical to the lower end 26 of the sleeve 21 shown at FIG. 4. With reference to FIG. 4, it will be remembered from previous discussion, that the lower end 26 includes a plurality of axially extending equally circumferentially spaced slots 25 which originate at lower end edge 27 and extend axially a short distance along the sleeve, and which slots define a plurality of flexible tabs or fingers 28 with inwardly bent tips 29. Lower end 226 has identical fingers 28.

Upper end230 of sleeve 221 is identical to lower end 226 and includes a plurality of flexible fingers 31 separated by slots in the same manner as described with reference to FIG. 4. Sleeve 221 can be formed from a flat piece of sheet metal by first cutting the slots at the upper and lower endswhile the sheet is in a flat state and by then rolling the sheet to cylindrical form and joining the edges along an interlocked double seam, such as the seam 32 shown at FIG. 3. When such a construction is used, the seam will be sealed with solder or a high melting temperature plastic cement so the body 222 is liquidtight. Sleeve 221 can also be formed from a seamlesstiibe of metal or othermaterial capable of resisting the temperatures and pressures of'the cooling system to which the compensating device is connected.

The upper end of compensating device 211 is closed by a cup-shaped member 38' identical to the member 38 described for FIG. 2. Hence, cup-shaped member 38' has a cylindrical sidewall 39 and a flat end wall 40. The sidewall 39 has a beveled inner end 41 to facilitate inserting the member 38 in upper end 230 of the compensating device 211. There is also a centrally located opening in end wall 40 which receives a radiator neck 42 that is secured and sealed to the end wall. The radiator neck 42 is identical to the radiator neck described for the compensating device of FIG. 2.

End member 38 is sealed to the upper end 230 of vacuum compensating device 211 by a sealing arrangement including a first gasket 37' and a second gasket 231. Gasket 37 takes the form of an endless band or tube of flexible material which is preferably resilient, is formed from high-temperatureresistant rubber, and has an axial length somewhat greater than the length of fingers 31. Gasket 231 is formed of a similar flexible and advantageously resilient material. In its preferred form, this gasket 231 is a short length of resilient tubing of the same material as tubular liner 24 of the embodiment of FIGS. 24.

Gasket 231 has a relaxed diameter approximately the same as the diameter of sleeve 221, and a length somewhat greater than twice the length of fingers 31.

End member 3% is connected to the upper end of sleeve 221 by first inserting gasket 37' in the sleeve and then inserting gasket 231 inside gasket 37'. Next, end member 38 is moved axially within the gaskets to the position of FIG. 12. Then, the outer end of gasket 231 is rolled down and over the top edge of sleeve 221 so a substantial length 232 of the gasket extends along the outside surface of sleeve 221. Then, clamp 47 is positioned around the gasket and tightened to seal end member 38 to the upper end of sleeve 221. It will be appreciated that gasket 37' extends axially inwardly of the sleeve beyond the inner ends of fingers 31 and that both ends of gasket 231 also extend inwardly of the inner ends of these fingers. The, when the band of clamp 47 is positioned with its lower edge slightly inwardly of the inner ends of finger 31, and the band is tightened, the resilient material of the gaskets is forced into the inner ends of the slots between the fingers to provide a liquidtight seal.

Lower end member 50' is identical to the lower end member 50 described at FIG. 2. This lower end member is cup-shaped and has a sidewall 51 and an end wall 52 with a central opening in which nipple 55 is inserted and secured by solder 56. End member 50 is sealed to the lower end of sleeve 221 in the same manner as described for end member 38'. The connection between end member 50 and the lower end of sleeve 221 includes a gasket 36 identical to the gasket 37' used at the upper end, and a gasket 234 identical to the gasket 231 used at the upper end of the sleeve. A clamp 47, when tightened, compresses the material of gaskets 36 and 234 to provide a Iiquidtight seal at the lower end of sleeve 22].

As shown at FIGS. 12-14, compensating device 211 is connected to an engine cooling system, including radiator 4, by a flexible tubular conduit which advantageously takes the form of a heater hose. One end of the hose is clamped to nipple 55 by a hose clamp 57, as shown at FIG. 12, and the other end of the hose is connected to connector assembly 89 (see FIG. 7 for the details of connector assembly 89) installed in upper tank 6 of the radiator. Filling neck 70 of radiator 4 is closed by the closure assembly 18 of FIG. 5.

FIG. 13 shows the level of coolant in compensating device 211 and radiator 4 when the coolant 74 is at its normal operating temperature, whereas FIG. 14 shows the level of the coolant in the compensating device and radiator when the coolant is cold and at ambient temperature. As shown at FIG. 13, both the radiator 4 and compensating device 211 are substantially full of coolant 74 when the coolant is at its nonnal operating temperature, There may, however, be a small amount of air 250 at the upper end of compensating device 211. This air functions as a cushion and is, of course, at the same pressure as the pressure in the cooling system.

Compensating device 211 is provided with a cap assembly identical to the cap assembly 17 described with reference to FIG. 2. This cap assembly includes a vacuum relief valve 62 (FIG. 12) which does not open until after a vacuum on the order of '/z-2 p.s.i. below atmospheric pressure is present in the cooling system. Since connector assembly 89 is connected to the top tank 6 of radiator 4, coolant will be drawn into the radiator to maintain the radiator full as the temperature of the coolant decreases. Hence, the coolant in compensating device 211 flows back into the radiator as the coolant in the engine block and radiator contracts on cooling. Initially, upon cooling, the air 250, which is present at the top of compensating device 211, expands to force the coolant back into the radiator. Upon further cooling, a slight vacuum is formed which will continue to draw the coolant into the radiator. If the vacuum in the cooling system reaches the relief pressure of valve 62, this valve will open and admit air to the compensating device to prevent excessive vacuum in the system.

When the engine is again started, there is still a slight vacuum in the cooling system. Hence, the initial expansion of the coolant, as a result of slight warming of the coolant, results in a pressure in the cooling system which is substantially lower than the pressure encountered in a cooling system without compensating device 211. The advantage of a lower pressure initially is that the hoses and other connections of the cooling system are not subjected to high positive pressures while these elements are cold. As the temperature of the coolant further increases with corresponding expansion, coolant is forced back into compensating device 211 until the pressure in the cooling system reaches its normal operating pressure. This operating pressure will be reached before the compensating device is filled with coolant returning from the radiator. I-Ience, pressure relief valve 61 may open to allow some of air 250 to escape to the atmosphere. Even though some air may be drawn into the compensating device each time the coolant cools and some air may be expelled from the compensating device each time the coolant heats up, the system operates in a very satisfactory manner to maintain the radiator full of coolant at all times.

Ideally, the system including the vacuum compensating device 211 will not admit additional air to the compensating device, and will not expel air from the compensating device unless the ambient temperature falls significantly, or there is a malfunction of the cooling system. Normally, when the ambient temperature does not fall below, say 60 F., the cushion of air 250 will merely expand during cooling, but the vacuum in the system will not be sufficient to open vacuum valve 62. When the coolant is heated, its temperature will not exceed the normal operating temperature of say F., unless conditions are abnormal. Hence, fresh air is normally not drawn into the system each time the coolant cools, as is the case with the conventional engine cooling system. Since fresh air contains oxygen which becomes entrained in the coolant, the admission of fresh air is quite detrimental to the system. With the vacuum compensating device 211, fresh air with oxygen is not normally admitted and deterioration of the cooling system is avoided. While some fresh air may enter the system as a result of seasonal changes of ambient temperature, only a small amount of oxygen enters the system, and there is little deterioration of the system. In the conventional cooling system, the vacuum relief valve opens whenever the pressure in the system is atmospheric. Hence, fresh air with oxygen is admitted each time the coolant cools.

FIG. 15 shows a chart of pressure v. temperature for a cooling system equipped with compensating device 211. It will be observed with reference to portion 255 of the curve (assuming an ambient temperature of 70) that the pressure in the system is l-Z p.s.i. below atmospheric when the coolant is cold. Then, as the coolant warms, the pressure in the system gradually increases as more coolant flows into the compensating device from the radiator as a result of coolant expansion and compresses air 250. If the pressure in the system exceeds the operating pressure, pressure relief valve 61 opens and the pressure in the system remains constant, with only some of the entrapped air 250 expelled through the pressure relief valve. Should overheating occur, excess pressure will normally be relieved by the pressure relief valve 61. In the event there is a rapid increase in pressure, such as caused by severe overheating and boiling of the coolant, the relief valve portion of the viewing cap closure assemblies 18 or 18', previously described, will also open to vent overpressure which may not be able to escape through the rather narrow conduit 15. By virtue of the two overpressure relief valves, one in the closure assembly 17 and the other in the closure assembly 18 or 18', damage to the cooling system as a result of overpressure is positively prevented even though one of the overpressure valves fails and remains closed. Similarly, when the closure assembly 18 is used with the system, damage to the system as a result of excess vacuum is also prevented because even if the relief valve 62 fails to open, the second relief valve provided by the band 81 will open.

It will also be observed with reference to FIGS. 5 and 6 that the upper end of cap 20 of closure assembly 18 is completely open so severe excess pressure, such as could be caused by coolant boiling, can escape directly through this opening rather than have to pass through the somewhat restricted overflow pipe opening of the radiator neck.

It will be apparent that the graphs of FIGS. 11 and 15 show pressure and temperature relationships for a cooling system in which both the compensating device and cooling system proper contain an optimum amount of coolant, and that these pressure and temperature relationships will vary with changes in the amount of coolant and with cooling systems of different volumes.

While several preferred embodiments of the vacuum compensating device of this invention have been shown and described in detail, including a rigid wall receptacle of preferred construction, it is to be understood that the rigid wall receptacle can have a seamless sidewall and end members secured to its ends in any manner, for example, by soldering or welding, to provide the rigid enclosure, and it is also contemplated that numerous changes can be made in these arrangements and constructions without departing from the intended scope of the invention as described and claimed herein.

What is claimed is:

l. A closed engine-cooling system comprising an engine having a cooling jacket forming a portion of the system;

a heat exchanger forming a portion of the system;

means connecting said cooling jacket to said heat exchanger for circulation of coolant from one to the other;

liquid coolant filling said system;

means defining an opening communicating with said heat exchanger and via which the system can be filled with coolant;

means sealing said opening during normal operation of said system;

compensating means to compensate for normal expansion and contraction of the coolant in said system due to normal temperature changes of the-system, and to maintain said system substantially full of coolant, said compensating means comprising a rigid enclosure including wall means of sufficient strength to contain the coolant at normal operating temperatures;

means connecting said compensating means in fluid communication with said system;

said enclosure having an opening in fluid communication with said system; means including vacuum relief valve means closing said en closure opening and allowing creation of a small vacuum within said system sufficient to cause coolant in said enclosure to return to said system and maintain the system full, upon cooling of said coolant; said vacuum relief valve means opening in response to a vacuum in said system above a predetermined value to prevent damage to said system; and

overpressure relief means connected to said enclosure to release pressure from said system above a predetermined value.

2. An engine cooling system according to claim 1 wherein said opening communicating with said heat exchanger is of the type adapted to receive a radiator cap and includes a receptacle, and

a sealing flange adjacent an end of said receptacle;

and wherein said means sealing said heat exchanger opening comprises a transparent viewing device having a seal element in engagement with said sealing flange, and

means urging said viewing device seal element into sealing engagement with said sealing flange;

said transparent viewing device extending into the coolant in said system to provide a visual indication of the level of the coolant adjacent said opening.

3. An engine cooling system according to claim 1 wherein said means connecting said compensating means in fluid communication with said system comprises a connector secured to said heat exchanger adjacent the top of said heat exchanger, and

a tubular conduit interconnecting said connector and said compensating means.

4. An engine cooling system according to claim 1 wherein said enclosure opening is of the type adapted to receive a radiator cap; and

said vacuum relief valve means and overpressure relief means cooperate with said opening to maintain said opening closed during normal operating conditions of said system.

5. An engine cooling system according to claim 4 wherein said vacuum relief valve means and said overpressure relief means comprise a preassembled unit securable to said enclosure adjacent its opening, and effective to seal said opening during normal operating conditions within said system.

6. An engine cooling system according to claim lwherein said overpressure relief means is connected to said enclosure; and

said means closing said opening communicating with said heat exchanger further includes second overpressure relief means: operable in response to pressure in said system slightly higher than the pressure to operate said first-mentioned overpressure relief means;

whereby, dangerous buildup of pressure within said system after release of said first-mentioned overpressure relief means is prevented by operation of said second overpressure relief means.

7. An engine cooling system according to claim I wherein said means sealing said opening communicating with said heat exchanger further includes second vacuum relief valve means arranged to open in response to a vacuum in said system higher than the vacuum required to operate said first-mentioned vacuum relief valve means;

whereby, collapse of delicate portions of said system is prevented by said second vacuum relief valve means in the event of malfunction of said first-mentioned vacuum relief valve means.

8. An enginecooling system according to claim I wherein said enclosure of said compensating means comprises an elongated sleeve;

said enclosure opening is at one end of the sleeve and is of the type adapted to receive a radiator cap, and means defining said enclosure opening and comprising a receptacle, and a sealing flange at the base of said receptacle;

said overpressure relief means being secured to said receptacle and including a pressure relief valve element insealing engagement with said sealing flange.

9. A closed engine cooling system of the type in which the pressure in the system is above atmospheric at normal operating temperatures, said system comprising an engine having a cooling jacket forming a portion of the system;

a heat exchanger forming a portion of the system;

means connecting said cooling jacket to said heat exchanger for circulation of coolant from one to the other;

liquid coolant completely filling said system;

means defining an opening communicating with said heat exchanger and via which the system can be filled with coolant;

means sealing said opening during normal operation of said system;

compensating means to compensate for normal expansion and contraction of the coolant in said system due to normal temperature changes of the system, and to maintain said system substantially full of coolant, said compensating means comprising a rigid enclosure including wall means of sufficient strength to contain the coolant at normal operating temperatures,

said enclosure having an opening adjacent its upper end,

and having an opening adjacent its lower end, nipple means secured at said opening adjacent the lower end of the enclosure and communicating with the interior of the enclosure, and a receptacle secured at said opening adjacent the upper end of the enclosure and communicating with the interior of the enclosure a conduit of a cross-sectional dimension substantially less than that of said enclosure and having one end secured to said nipple means and the other end secured to said heat exchanger, whereby said compensating means communicates with said system via said conduit; means including vacuum relief valve means and overpressure relief valve means coacting with said receptacle and closing said enclosure opening during normal operating conditions in the system, said vacuum relief valve means opening in response to a vacuum in said system to prevent damage to the system and to cause coolant in said enclosure to return to said system and maintain the system full, upon cooling of said coolant; said overpressure relief means releasing pressure from said system above a predetermined value. 10. A cooling system according to claim 9 wherein said enclosure is cylindrical and elongated. 11. A cooling system according to claim 9 wherein clamp means secures said nipple means to the lower end of said enclosure. 12. A cooling system according to claim 9 wherein clamp means secures said receptacle to the upper end of said enclosure. 13. A cooling system according to claim 9 wherein said heat exchanger opening includes a receptacle presenting a flange and an overflow opening above the flange; and said means sealing said opening includes a closure assembly comprising a seal element engaging said flange, spring means engaging said seal element and urging the seal element against the flange, and a cap secured to the receptacle and urging the spring toward the seal element; said cap having a large opening therein to allow escape of vapor from the system in the event of overheating. 14. A cooling system according to claim 9 wherein said conduit is secured to said heat exchanger by a nipple connected to the heat exchanger at a location adjacent its upper end and spaced from said heat exchanger opening. 15. A cooling system according to claim 14 wherein said heat exchanger has an upper tank; said heat exchanger opening is formed in said upper tank;

and said nipple extends through a wall of the upper tank. 16. A cooling system according to claim 9 wherein said means sealing said heat exchanger opening includes closure means including overpressure and vacuum relief valve means. 

1. A closed engine-cooling system comprising an engine having a cooling jacket forming a portion of the system; a heat exchanger forming a portion of the system; means connecting said cooling jacket to said heat exchanger for circulation of coolant from one to the other; liquid coolant filling said system; means defining an opening communicating with said heat exchanger and via which the system can be filled with coolant; means sealing said opening during normal operation of said system; compensating means to compensate for normal expansion and contraction of the coolant in said system due to normal temperature changes of the system, and to maintain said system substantially full of coolant, said compensating means comprising a rigid enclosure including wall means of sufficient strength to contain the coolant at normal operating temperatures; means connecting said compensating means in fluid communication with said system; said enclosure having an opening in fluid communication with said system; means including vacuum relief valve means closing said enclosure opening and allowing creation of a small vacuum within said system sufficient to cause coolant in said enclosure to return to said syStem and maintain the system full, upon cooling of said coolant; said vacuum relief valve means opening in response to a vacuum in said system above a predetermined value to prevent damage to said system; and overpressure relief means connected to said enclosure to release pressure from said system above a predetermined value.
 2. An engine cooling system according to claim 1 wherein said opening communicating with said heat exchanger is of the type adapted to receive a radiator cap and includes a receptacle, and a sealing flange adjacent an end of said receptacle; and wherein said means sealing said heat exchanger opening comprises a transparent viewing device having a seal element in engagement with said sealing flange, and means urging said viewing device seal element into sealing engagement with said sealing flange; said transparent viewing device extending into the coolant in said system to provide a visual indication of the level of the coolant adjacent said opening.
 3. An engine cooling system according to claim 1 wherein said means connecting said compensating means in fluid communication with said system comprises a connector secured to said heat exchanger adjacent the top of said heat exchanger, and a tubular conduit interconnecting said connector and said compensating means.
 4. An engine cooling system according to claim 1 wherein said enclosure opening is of the type adapted to receive a radiator cap; and said vacuum relief valve means and overpressure relief means cooperate with said opening to maintain said opening closed during normal operating conditions of said system.
 5. An engine cooling system according to claim 4 wherein said vacuum relief valve means and said overpressure relief means comprise a preassembled unit securable to said enclosure adjacent its opening, and effective to seal said opening during normal operating conditions within said system.
 6. An engine cooling system according to claim 1 wherein said overpressure relief means is connected to said enclosure; and said means closing said opening communicating with said heat exchanger further includes second overpressure relief means operable in response to pressure in said system slightly higher than the pressure to operate said first-mentioned overpressure relief means; whereby, dangerous buildup of pressure within said system after release of said first-mentioned overpressure relief means is prevented by operation of said second overpressure relief means.
 7. An engine cooling system according to claim 1 wherein said means sealing said opening communicating with said heat exchanger further includes second vacuum relief valve means arranged to open in response to a vacuum in said system higher than the vacuum required to operate said first-mentioned vacuum relief valve means; whereby, collapse of delicate portions of said system is prevented by said second vacuum relief valve means in the event of malfunction of said first-mentioned vacuum relief valve means.
 8. An engine cooling system according to claim 1 wherein said enclosure of said compensating means comprises an elongated cylindrical sleeve; said enclosure opening is at one end of the sleeve and is of the type adapted to receive a radiator cap, and means defining said enclosure opening and comprising a receptacle, and a sealing flange at the base of said receptacle; said overpressure relief means being secured to said receptacle and including a pressure relief valve element in sealing engagement with said sealing flange.
 9. A closed engine cooling system of the type in which the pressure in the system is above atmospheric at normal operating temperatures, said system comprising an engine having a cooling jacket forming a portion of the system; a heat exchanger forming a portion of the system; means connecting said cooling jacket to said heat excHanger for circulation of coolant from one to the other; liquid coolant completely filling said system; means defining an opening communicating with said heat exchanger and via which the system can be filled with coolant; means sealing said opening during normal operation of said system; compensating means to compensate for normal expansion and contraction of the coolant in said system due to normal temperature changes of the system, and to maintain said system substantially full of coolant, said compensating means comprising a rigid enclosure including wall means of sufficient strength to contain the coolant at normal operating temperatures, said enclosure having an opening adjacent its upper end, and having an opening adjacent its lower end, nipple means secured at said opening adjacent the lower end of the enclosure and communicating with the interior of the enclosure, and a receptacle secured at said opening adjacent the upper end of the enclosure and communicating with the interior of the enclosure a conduit of a cross-sectional dimension substantially less than that of said enclosure and having one end secured to said nipple means and the other end secured to said heat exchanger, whereby said compensating means communicates with said system via said conduit; means including vacuum relief valve means and overpressure relief valve means coacting with said receptacle and closing said enclosure opening during normal operating conditions in the system, said vacuum relief valve means opening in response to a vacuum in said system to prevent damage to the system and to cause coolant in said enclosure to return to said system and maintain the system full, upon cooling of said coolant; said overpressure relief means releasing pressure from said system above a predetermined value.
 10. A cooling system according to claim 9 wherein said enclosure is cylindrical and elongated.
 11. A cooling system according to claim 9 wherein clamp means secures said nipple means to the lower end of said enclosure.
 12. A cooling system according to claim 9 wherein clamp means secures said receptacle to the upper end of said enclosure.
 13. A cooling system according to claim 9 wherein said heat exchanger opening includes a receptacle presenting a flange and an overflow opening above the flange; and said means sealing said opening includes a closure assembly comprising a seal element engaging said flange, spring means engaging said seal element and urging the seal element against the flange, and a cap secured to the receptacle and urging the spring toward the seal element; said cap having a large opening therein to allow escape of vapor from the system in the event of overheating.
 14. A cooling system according to claim 9 wherein said conduit is secured to said heat exchanger by a nipple connected to the heat exchanger at a location adjacent its upper end and spaced from said heat exchanger opening.
 15. A cooling system according to claim 14 wherein said heat exchanger has an upper tank; said heat exchanger opening is formed in said upper tank; and said nipple extends through a wall of the upper tank.
 16. A cooling system according to claim 9 wherein said means sealing said heat exchanger opening includes closure means including overpressure and vacuum relief valve means. 